1. Field of the Invention
The present intention relates to a dynamic pressure bearing apparatus, and more specifically a dynamic pressure bearing apparatus which is suited for use in a light deflecting apparatus such as a laser beam printer or a bar-code reader.
2. Related Background Art
A laser beam printer or a bar-code reader uses a light deflecting apparatus for scanning a medium to be scanned with a laser beam. In such a light deflecting apparatus a rotating polyhedral mirror which is rotated at a high speed is attached to a rotating shaft rotatably supported by a bearing Conventional bearing frequently used as such a bearing is a dynamic pressure bearing which can rotate stably and smoothly. Furthermore, dynamic pressure bearings are used widely in information storage appliances such as optical disks, magnetic disks and the like as a bearing for supporting a disk rotating at a high speed.
FIG. 1 is a schematic sectional view showing an example of main members of a conventional light deflecting apparatus such as that described above. In FIG. 1, a rotating shaft 101 is rotatable supported in a bearing slot formed in a sleeve 102. At a lower end of the sleeve 102, a fixed plate 103 is fixed to seal the above-described bearing slot and a thrust plate 104 is disposed on the fixed plate 103. Between an inside surface of the bearing slot of the sleeve 102 and an outside surface of the rotating shaft 101 and between the thrust plate 104 and an end surface of the rotating shaft 101, oil is filled as an operating fluid for generating a dynamic pressure. Furthermore, the end surface of the rotating shaft 101 is made of a material having low frictional resistance and composes a thrust bearing together with the thrust plate 104.
A flange member 110 is fixed to an upper portion of the rotating shaft 101. A rotating polyhedral mirror 111 having a reflecting surface 111a is mounted on the flange member 110. This rotating polyhedral mirror is pressed by a pressing spring so as to be coupled integrally with the flange member 110 and a rotor 112.
The rotor 112 has a permanent magnet 112a and a yoke 112b supporting the permanent magnet 112a. On the other hand, a circuit board 114 is fixed to the sleeve 102 and a stator core 113b of a stator 113 is erected and supported on the circuit board 114. A stator coil 113a wound around the stator core 113b is opposed to the permanent magnet 112a of the rotor 112, and a motor which rotatingly drives the rotating polyhedral mirror 111 is composed of the stator coil 113a and the permanent magnet 112a. 
An oil reservoir 102a is formed on a top end portion of the bearing slot of the sleeve 102, thereby reserving a redundancy for rampage of a liquid surface of the oil in the bearing slot. Furthermore, large-diameter portions are formed also at the lower end portion and in a middle portion of the sleeve 102 so as to form relief portions 102b and 102c for reducing a loss of a dynamic pressure of the oil. Furthermore, herringbone dynamic pressure generating grooves 105a and 105b are formed on an outer circumferential surface of the rotating shaft 101 between the oil reservoir 102a at the top end and the relief portion 102c in the middle portion and between the relief portion 102c in the middle portion and the relief portion 102b at the lower end, respectively
A spiral groove (not shown) is formed on a top surface of the thrust plate 104. An upper end of the rotating shaft 101 protrudes higher than the bearing slot of the sleeve 102 to compose a coupled portion of the rotating polyhedral mirror 111 together with the flange member 110.
When the rotating shaft 101 rotates in the dynamic pressure bearing apparatus which is configured as described above, a dynamic pressure is generated in the oil by a function of the dynamic pressure generating grooves 105a and 105b formed in the bearing slot of the sleeve 102 and the rotating shaft 101 is rotated in a condition where the rotating shaft 101 is not in contact with the bearing slot of the sleeve 102. Also in a thrust direction, a dynamic pressure is generated by a function of a spiral groove formed on the thrust plate 104, whereby the rotating shaft 101 is supported in a floated condition.
In case of using a liquid such as oil as an operating fluid for a dynamic pressure bearing, however, the above-described conventional technology may allow air to be involved in the operating fluid when the sleeve 102 is fitted over the shaft 101 at an initial assembling step of the production. When the apparatus is heated by rotation or installed at a location kept at a low pressure such as a highland, if the involved air is stagnant in a large amount in the relief portions 102b and 102c, the involved air penetrates from the relief portions 102b and 102c into a bearing gap of the dynamic pressure bearing. As a result, the air which is formed into bubbles may carry out the oil when the air is exhausted outside from an opening of the bearing.
When the oil leaks out from the opening of the bearing as described above in a condition of use where a light deflecting apparatus is repeatedly started and stopped, the oil goes along the flange member 110 and the yoke 112b, and is splashed by centrifugal forces generated by rotations of the flange member 110 and the yoke 112b, thereby posing a problem to cause malfunctions of appliances
In order to solve a problem as described above, Japanese Patent Application Laid-Open No. 6-311696 discloses a method for providing a rotating shaft with an oil leakage preventive member. Furthermore, Japanese Patent Application Laid-Open No. 8-75011 discloses a method for disposing an oil absorbing sheet which absorbs leaked oil.
However, both the methods described above have problems of showing an insufficient leakage preventive effect and making assembling steps complicate.
An object of the present invention is to solve the problems of the above-described prior art and provide a dynamic pressure bearing apparatus having high performance and excellent stability without hindering operations of appliances due to leaked oil.
An object of the present invention is to provide a dynamic pressure bearing apparatus comprising:
a rotating shaft inclined in a predetermined direction from a vertical direction;
a sleeve rotatably supporting the rotating shaft;
an operating fluid for generating a dynamic pressure, the operating fluid being filled in a gap formed between the sleeve and the rotating shaft; and
capturing means for capturing the operating fluid leaked from the gap, the capturing means being disposed on an outside surface of the sleeve in the predetermined direction.
Another object of the present invention is to provide a rotating apparatus comprising the dynamic pressure bearing apparatus as described above and a motor for rotating the rotating shaft.
Still another object of the present invention is to provide a light deflecting apparatus comprising the rotating apparatus as described above and a rotating polyhedral mirror attached to the rotating shaft.
A further object of the present invention is to provide a laser beam printer comprising a light source for emitting a laser beam, the above-described light deflecting apparatus for deflecting the laser beam emitted from the light source a photosensitive member and a scanning lens for condensing on the photosensitive member the laser beam deflected by the light deflecting apparatus.